This invention relates to poly (carbonyl fluoride) oligomers and to an improved method for their preparation. In a more particular aspect, this invention relates to the photo-oxidation of F-3-methylbutene-1 in the presence of bis(trifluoromethyl)trioxide as a reaction initiator to form poly (carbonyl fluoride) oligomers.
s-Triazines having perfluorinated polyether substituents of the type illustrated by the following general formula: ##STR1## where R.sub.f =CFXCF.sub.2 O(CFXCF.sub.2 O).sub.n CFX and x=CF.sub.3 or F. These triazines have been found to be particularly useful as candidates for high temperature fluids which serve as base stocks for advance hydraulic fluids, coolants, gas turbine engine oils and greases. These fluids possess very desirable properties such as inherent stability at temperatures up to 700.degree. F., excellent compatability with metals up to 650.degree. F., good lubricity and non-flammability. These characteristics make these fluids excellent candidates for a wide temperature range, non-flammable, hydraulic fluid. However, the low temperature rheological properties and moderately high volatility of these fluids have been their only deficiencies. These deficiencies can be improved, however, by increasing their oxygen to carbon ratio (o/c). This increase in o/c ratio can be accomplished by the use of poly (carbonyl fluoride) oligomers. The use of these materials involves disadvantages, however, because of the low yield of selected oligomers and their low molecular weight when produced by prior art methods of synthesis.
In an attempt to overcome the problems associated with prior art methods, it was found that the photo-oxidation of F-3-methylbutene-1 in the presence of ultraviolet radiation using a low pressure mercury lamp produced the desired oligomers with only an insignificant amount of fluoroformate terminated material being produced as a reaction by-product. In previously known methods of synthesis, fluoroformate terminated material was produced in significant amounts and had to be removed before the oligomers could be utilized in the synthesis of the desired s-triazine high temperature fluids. The oxidation of F-3-methylbutene-1, however, overcame this problem. Nevertheless, further attempts at improving the synthesis of these desirable oligomers was undertaken and a continuing research effort was maintained. As a result of this effort, it was found that the rate of the photo-oxidation reaction of F-3-methylbutene-1 could be unexpectedly increased twofold by utilizing a minor amount of bis(trifluoromethyl) trioxide as a reaction initiator. This increase in reaction rate further increased the utilization of these oligomers in the synthesis of the s-triazine fluids.